Portable heater



FIG. 1 is a top perspective view of the portable heater design;

FIG. 2 is a bottom perspective view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a top view thereof;

FIG. 6 is a bottom view thereof;

FIG. 7 is a rear view thereof; and,

FIG. 8 is a front view thereof.

The broken lines illustrate portions of the portable heater which form no part of the claimed design. 

The ornamental design for a portable heater, as shown and described. 